Cylinder Head Comparison
This chart is a collection of published flow numbers for different types of cylinder heads. They are sorted by max intake flow at 0.500" lift, which is frankly a completely arbitrary way of doing it. Our reasoning is that we are looking for high flow at higher rpm. But that doesn't mean that heads higher on the chart are necessarily "better". As a good example of this, note how the W2 cylinder heads are ranked higher than the Edelbrock heads, because at 0.500" lift the intake side flows better. But if you compare the heads across the board, the Edelbrock heads outflow the W2 heads at almost every other point during the cycle. Chances are, the Edelbrock heads probably provide more useable horsepower even if the peak numbers are slightly off. So, it's important to study the complete chart, not just the single data point.

Now, everyone always says that cylinder head numbers are not comparable, that the same set of heads can flow differently on different benches. That is like saying that dragstrip timeslips from two different tracks are not comparable. While it is true that you wouldn't want to treat the exact numbers as gospel, having a look at the flow table at least gives a general idea of what certain heads are capable of producing.

Head Type
1994 W2 Econo Mildly Ported N/A60127184232274302 N/A50105154185200208
2915J Fully Ported, 2.02" Valves N/A62130186239272277 N/A52101132166173178
3994 W2 "Econo" N/A59122182229263265 N/A51110154173176174
4Edelbrock Mildly Ported N/A72135191233260260 N/A69113142164176183
5587 Fully Ported, 2.02" Valves 3263126181230253241 245795132132160179
6W2 Mopar Perf. N/A69120173215244254 N/A63113142148151151
7Edelbrock N/A72126179224239242 N/A66110139158170176
8051 Fully Ported, 2.02" Valves 4077137186225228224 2752104140159168175
9894 Stock 340X 3258125172208221210 224595122135140142
10915J Stock N/A66123170206220216 N/A63110135145148148
11140 Magnum R/T 3470137181209211211 2462111142163168171
12137 Magnum 3160118165195209205 235499131167138138
13596 Stock 2753107159185199193 224889114121123124
14051 Stock 3050113165188193189 234997123133137137
15576 High Swirl 3162112160182192187 235599119126128130
16587 Stock 2752107162195191192 224687112121124126

1. Tony West's Rollin' Thunder website,
2. Moparts, Carl's Tech Archive, "974 Flow Test Results, Part 2", 2-19-2002,
3. Tony West's Rollin' Thunder website,
4. High Performance Mopar magazine, 7-1999.
5. Car Craft magazine, 2-2002.
6. High Performance Mopar magazine, 7-1999.
7. High Performance Mopar magazine, 7-1999.
8. Mopar Muscle magazine, 1-2000 & 2-2000.
9. Mopar Muscle magazine, 1-2000 & 2-2000.
10. High Performance Mopar magazine, 7-1999.
11. Car Craft magazine, 2-2002.
12. Car Craft magazine, 2-2002.
13. Car Craft magazine, 2-2002.
14. Mopar Muscle magazine, 1-2000 & 2-2000.
15. Car Craft magazine, 2-2002.
16. Car Craft magazine, 2-2002.

Factory Casting Cheat Sheet

051     318/360     1977-83
137     Magnum
140     Magnum R/T
308     360 Swirl?  1989-93
587     340/360     1973-74; 1976
596     318/360     1977-83
915     340/360     1970-72
974     360         1975-76
994     MP W2 Econo
As with anything made by the factory, it's important to keep in mind that factory tolerances are not exactly what we'd call "precision machining". Tony West's website has a page that compares several 915J heads and he shows a 50 cfm difference at 0.500" lift between the worst heads and the best. Of course, Mr. West doesn't provide citations for his flow numbers, so it's not easy to verify them. But still, the evidence definitely indicates that factory castings with 2.02" intake valves and a really thorough porting job are able to return flow numbers in the same ballpark as the best performance heads. The question then is primarily one of cost. Who is doing the porting job? The home porter could save a bundle by spending a couple of days cleaning up stock castings. But someone who is not inclined to get dirty might find it more economical to buy the performance heads rather than pay labor charges on a substantial reworking.

Considering the variation in the flow numbers of stock castings, it might be a good idea to have any set of stock castings flow tested after cleaning but before modifying. That way there will be a baseline for those specific heads, eliminating any guesswork about performance gains.

We've also presented a factory casting number cheat sheet. Most casting number sheets list the data chronologically, which is least helpful when you've got a set of heads sitting at a swap meet and you wonder what they fit. Using this sheet, just take the last three digits of the casting number and see where they came from. This sheet only lists heads that were installed on 360 engines, though as the chart shows, the same castings were often used on more than one engine type. Our data after 1983 remains sketchy so we will add to the chart as we learn more.